Thursday, 02 October 2014
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Collaboration set to design motors for giant solar aircraft

The electric motors that will propel Boeing’s planned giant solar aircraft will be designed by researchers at Newcastle University in collaboration with Qinetiq.

The team secured the latest contract after its successful demonstration of the Zephyr solar aircraft, which last year achieved a record-breaking two-week, non-stop flight.

Boeing’s SolarEagle, which will have a wingspan of 120m, will take this a step further by aiming to remain in the air continuously for five years while feeding back data from the skies.

Flying at a height of more than 60,000ft in temperatures below -60°C, the project will present significant challenges for the team, but Prof Barrie Mecrow of Newcastle said they will take some lessons from Zephyr.

‘We learned how to operate these machines at very low temperatures and to cope with things you perhaps initially don’t expect — for example, where you have bearings, the grease in the bearing goes solid.

‘Also with the electronics, we not only have to worry about the large components, we have to think about power used by the microprocessor for example, which uses one and a half watts.’

The SolarEagle will use around 19 electric motors, which will have to be scaled up from those of the Zephyr — although as Mecrow explained larger electric motors generally achieve greater efficiencies. The group believes it can improve on Zephyr’s 85 per cent conversion rate to anywhere up to around 98 per cent.

‘We’re really trying to squeeze everything we can out of the system,’ Mecrow said.

Aircraft such as the SolarEagle will have a range of applications, from military reconnaissance and communications platforms to environmental monitoring and disaster-relief support.

One key advantage is their persistence over a location, which is in contrast to low-Earth orbiting satellites that come and go in a swift pass overhead and unmanned drones now operated by the military that need to return to base at regular intervals for refuelling.

The US Defense Advanced Research Projects Agency (DARPA) is contributing $89m (£56m) to the programme with Boeing providing additional investment funding.

The programme, which will culminate with a demonstration flight, is due to be completed in early 2014 and the Newcastle team hopes to have the first two prototypes of the aircraft’s motors ready to test in the next six months.

’It’s fantastic that they’ve decided to work with Qinetiq and Newcastle to build their solar aircraft because it acknowledges the world-leading expertise we have in this field here in the UK,’ said James Widmer, who coordinates the Centre for Advanced Electrical Drives at Newcastle University.


Readers' comments (2)

  • As the person who started the voyage into system-level efficiency in housing processes (furnace fan systems were often <10% efficient), I am sure that the team can do great things. Several things to watch for are:
    * oversizing often means that the motor does not work at its optimum efficiency;
    * keep checking use and losses at the system level;
    * look at the waste Watts rather than the gross and it becmes easier to see what to correct;
    * realize that any flow process can have an 'absolute' system efficiency defined, rather than just a relative one (in SI, volumetric flow rate times pressure drop in Pa is flow Watts);
    * ask around to have outsiders review both design and performance figures - we old farts love to help for free.

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  • Like the Zephyr, will this aircraft also use the proven industry-leading light-weight thin-film solar laminate panels made by Uni-Solar Ovonics, a subsidiary of the Michigan company Energy Conversion Devices [ticker symbol ENER]?

    I would expect so.

    Uni-Solar's website: http://www.uni-solar.com/?s=zephyr

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